With Cleary he targeted News International, 20th Century Fox, the Arizona State Police, Nintendo, Sony and the right-wing Westboro Baptist Church, among several other sites.

Cleary said he also attacked the website of the CIA and the US Air Force with the help of other members of the Anonymous-related hacking group.

But appearing at Southwark Crown Court on Monday, both Davis and Cleary denied charges of taking confidential data and publishing it on hacking forums including the Pirate Bay and PasteBin.

In total the pair pleaded guilty to two counts of 'conspiracy to do an unauthorised act or acts with intent to impair, or with recklessness as to impairing, the operation of a computer or computers'.

They each pleaded not guilty to encouraging or assisting an offence, contrary to section 45 of the Serious Crime Act 2007, and encouraging or assisting offences, contrary to section 46 of the Serious Crime Act 2007.

Cleary also pleaded not guilty to four charges under sections 1 and 3 of the Computer Misuse Act 1990.

Cleary was arrested in June 2011, and later jailed after breaching his bail conditions when he is said to have contacted a hacker known as Sabu who was working with the FBI.

The United States has said that it will not seek to extradite Cleary and that they accept he would face trial in the UK.